1. Field of the Invention
The present invention belongs to a technical field in relation with a steel wire rod, particularly to a technical field in relation with a steel wire rod excellent in scale adhesion properties (the scale is hard to be detached) during cooling after hot rolling and during storage and transportation (during storage, during transportation), and excellent in scale detachment properties during mechanical descaling.
2. Description of the Related Art
On the surface of the steel wire rod (hereinafter referred to also as “wire rod”) manufactured by hot rolling, the scale is formed, and it is necessary to remove the formed scale prior to wire drawing and the like of secondary working of the wire rod. In wire drawing of the wire rod in recent years, from the viewpoints of pollution problems and cost reduction, the method of removing scale is changing from the acid washing method by batches to the mechanical descaling method. Therefore, it is desired to develop the wire rod whose scale can be easily detached in mechanical descaling (hereinafter referred to also as “MD”), in other words, the wire rod with the scale characteristics excellent in MD properties.
From such viewpoints, the technologies described below have been disclosed as the manufacturing methods of the wire rod having the scale characteristics excellent in MD properties.
(1) The method for decreasing the residual scale quantity in the wire rod by increasing FeO ratio or decreasing Fe3O4 ratio in the scale and increasing the thickness of the scale (the Japanese Unexamined Patent Application Publication No. H4-293721, the Japanese Unexamined Patent Application Publication No. H11-172332).(2) The method for lowering the boundary face roughness in order to prevent the anchor effect by biting in of the scale (the Japanese Unexamined Patent Application Publication No. H8-295992).(3) The method for improving the scale detachment properties by including the blow hole in the scale and lowering the strength of the scale (the Japanese Unexamined Patent Application Publication No. H10-324923, the Japanese Unexamined Patent Application Publication No. 2006-28619).